Unreviewed assertion fix.

RegExpCachedResult::m_reified is now the dedicated member that knows whether
the result was reified into an array or not. Check that instead of m_result
which is now single-purpose.

* runtime/RegExpCachedResult.cpp:
(JSC::RegExpCachedResult::setInput):

git-svn-id: http://svn.webkit.org/repository/webkit/trunk@175372 268f45cc-cd09-0410-ab3c-d52691b4dbfc